한국소음진동공학회 2012년 춘계학술대회논문집, pp.208~209

VEHICLE DESIGN

A comprehensive design cycle for car engine sound: from processing to software component to be integrated in the audio system of the vehicle. François Orange 1 and Patrick Boussard 3 GENESIS , BP69, 13545 Aix en Provence Cedex 4 – France

ABSTRACT This paper describes a comprehensive process and range of design tools and components for providing Improved perception of engine sound for mass production vehicles by the generation of finely tuned engine .

Figure 1‐ Example of order 2 enhancement ANALYSIS OF ENGINE SOUND The engine sound depends on the following parameters: • engine architecture: 4 or 6‐ configurations on an inline engine, V engine, two or four‐stroke engine, reciprocating or rotary engine • engine’s fuel type (gasoline, Diesel…) • rotation speed (RPM) • engine load or acceleration pedal position (throttle ) • gear ratio (rarely) • applied on the engine by the wheels (rarely) Preliminary work consists in recording and analyzing the natural sound of the vehicle: 1st step : time‐ representation of a 2nd or 3rd gear ‐ acceleration with Wide Open Throttle (WOT) 2nd step: order extraction 3rd step: throttle position influence

SYNTHESIS OF ENGINE SOUND Genesis sound synthesis algorithm The algorithm is based on a sum of pure tones with the following parameters: • The frequency of each pure tone is a multiple of the engine’s frequency. Example for a 4 cyl – 4 stroke engine: orders and half orders • The level of each is given by the order analysis matrix: order rank, level, RPM. Between 2 measurement points we do a linear interpolation • In the real‐time implementation , GeneBOX, we get the engine’s RPM from the CAN Bus and update the synthesis parameters every 10ms • Only the desirable part of order is generated in order to complement the natural orders from the engine

SOUND DESIGN FOR CONSTANT SPEED • With the harmonic sound control panel, it is possible to modify the level of each harmonic in real time for a given RPM and then to control the perception of the engine sound.

208│ • A sporty car has a general higher level of harmonics than a normal car • The amplification of consecutive harmonics (i.e. 3.5, 4, 4.5, 5) increase the roughness of the sound and the sportive feeling of the car • The amplification of harmonics 4, 6, 8 increase the sharpness of the sound and sportive feeling: when RPM changes, it seems to go higher • The amplification of low frequency harmonics (2, 3, 4) enhances the feeling of a power of the engine • The amplification of harmonics 3, 6, 9, 12 of a 4‐cylinder engine give the feeling of a 6‐ cylinder engine

SOUND DESIGN FOR ACCELERATION • Much more than in constant speed, sound design of engine will be appreciated by the driver during acceleration. For this, the software allows to modify each harmonic for a range of RPM. • The progression map of the throttle position can be edited to determine the sound according to the eway th driver accelerates • Various styles of sound design can be experimented and tested by listeners

VALIDATION AND MASS PRODUCTION SOLUTION • The GeneBOX allows to test the sound synthesis in real cars and real driving conditions. Several setup for different cars can be uploaded on the device. • experiments can be led in listening room to validate the final sound design selected. • Finally the synthesis algorithm and the sound data esets ar implemented as software components in the audio system of the car.

CONCLUSION Advantages of Engine Active Sound Design • Cost & weight save cost and weight on exhaust and intake design based solutions • Design work reduces constraints during the design, more creativity for the sound • Flexibility the sound can be easily adapted to each vehicle, and later in the design process • Friendliness possibility of data base to be selected by the driver • Adaptation the sound can be adapted to various driver preferences and driving conditions • Environment no impact out of the car • Performance contributes to reduce the mass of the vehicle, its CO2 emission and improve its performance

Advantages of the described approach  No hardware requirement from the vehicle: uses the standard audio system and its  Ease of sound design  Easy move to mass production by the use of standard software components  Very good control of the development cost and time  May improve greatly the sound perception with only a small increase of overall sound level  Ideally suited for mid‐range vehicles with 4 cylinder

Application for EV and HEV  This method may be transposed for the generation of interior as well as exteriors sound for electric and hybrid vehicles

│209